Exercise affects the gastrointestinal tract, so people may sometimes experience nausea after a workout.
Those who occasionally get this symptom may find that changing their workout type and their eating or drinking habits helps resolve it. In some cases, consistent nausea after exercising may indicate an underlying health condition.
In this article, we look at the causes of nausea after exercise, steps to treat and prevent it, and when to see a doctor.
According to a 2013 review, GI symptoms are common in sports players, with various studies estimating that they affect 20–70% of athletes.
These symptoms appear to affect endurance athletes the most. As many as 83% of marathon runners report a link between GI symptoms and running.
Upper GI tract symptoms are more common among cyclists than runners. They may include:
- gastroesophageal reflux
Runners tend to experience lower GI tract symptoms, such as:
- stomach cramps
- GI bleeding
However, nausea is especially common in extreme endurance sports, such as ultramarathon running. Up to 90% of competitors may experience GI symptoms during endurance races.
Some of the main causes of exercise-induced nausea and gastrointestinal (GI) symptoms include:
- reduced blood flow to the digestive tract and abdominal organs
- delayed gastric emptying
- hyponatremia, which is a lack of sodium in the blood
In rare cases, exercise-induced nausea may be due to an underlying condition, such as:
- kidney failure
- anaphylaxis after eating
- gallbladder scar tissue
- ischemic bowel disease, in which there is not enough blood flow to the small intestine
- hemorrhagic gastritis
During exercise, there may be a reduction of up to 80% in the blood flow to the abdominal organs, as the body sends more blood to the muscles and skin. This effect may result in nausea, vomiting, stomach pain, and diarrhea.
Eating too soon before a workout can also cause nausea.
A study from 2001 in 12 healthy participants found that exercising immediately after eating caused higher levels of nausea than waiting 60 minutes before exercising.
The researchers also found that nausea levels were higher during high intensity workouts than during low intensity workouts.
Moderate exercise appears to have little effect on gastric emptying, whereas high intensity or intermittent exercise may slow down gastric emptying and cause nausea or other GI symptoms.
According to a 2014 article in Sports Medicine, people may be able to reduce nausea after exercising by drinking a sports drink with multiple transportable carbohydrates, such as glucose and fructose.
The authors note that it may also help to take supplements that help the body make nitric oxide. Increasing the availability of this compound may help increase blood flow to the abdominal organs.
However, the authors also state that scientists need to do more research on these potential treatments.
Anecdotal sources suggest that people may be able to resolve their symptoms by walking slowly after a workout or lying flat on the back and lifting the feet higher than the stomach.
People may be able to take steps to reduce or prevent nausea when exercising. These include:
- eating a diet with adequate fiber to maintain gut health but avoiding foods high in fiber before exercising
- avoiding slow-digesting foods, such as protein, fat, and milk products, before exercising to ensure quicker gastric emptying
- avoiding taking aspirin and other nonsteroidal anti-inflammatory drugs when exercising, as these may increase GI symptoms
- refraining from consuming foods and drinks high in fructose, particularly high fructose beverages, unless they also contain glucose
- staying well-hydrated before and during exercise to avoid dehydration, which can worsen GI symptoms
- consuming carbohydrate-rich foods with a higher water content or drinks with a lower carbohydrate concentration
A person can experiment with nutrition plans to determine which foods and drinks suit them best when exercising and how much time they need to leave between eating and exercising.
People may also find that it helps to warm up and cool down properly before and after exercising. Beginning with lower intensity workouts and gradually building up is also a sensible approach.
Nausea and other GI symptoms during exercise can be uncomfortable. However, they are normal and usually pose no health risk.
People may be able to prevent exercise-induced nausea by altering their eating and drinking patterns, properly warming up and cooling down, and reducing the intensity of their workouts.
If altering eating and workout habits is not effective, or people experience long lasting symptoms or frequent nausea, they should see a doctor.
People should also see a doctor if they experience severe symptoms, such as blood in the stool, vomiting blood, black or tarry bowel movements, or severe stomach pain. These symptoms may indicate a more serious underlying health issue.
When people exercise, less blood reaches the digestive tract, and this can result in nausea and other uncomfortable GI symptoms. Higher intensity workouts are more likely to have this effect.
Other potential causes of these symptoms include eating too soon before exercising, dehydration, and an imbalance of electrolytes.
People may be able to treat or prevent nausea after exercising by switching to lower intensity workouts or not exercising too soon after eating.
If adjustments to exercise habits do not help reduce nausea, or if people have severe or long lasting symptoms, they should see a doctor.